JPH05275097A - Fuel cell generating device - Google Patents

Abstract

PURPOSE:To prevent the operation under shortage of hydrogen by operating the utilization factor of hydrogen accurately. CONSTITUTION:Hydrogen concentration detectors 9 and 10 detect each hydrogen concentration of the gas on the inlet side and the outlet side of an anode pole 2, and output each hydrogen concentration detection signal. The operation means of a controller 8B operates the utilization factor of hydrogen from the hydrogen concentration detection signal, and compares specified reference value set signal 11 with a hydrogen utilization factor signal, and outputs an alarm signal 13 to an alarm display 12 and a system stop signal 15 to a system stop controller 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator suitable for preventing hydrogen shortage operation of an anode electrode during load operation so as not to adversely affect the battery.

[0002]

2. Description of the Related Art In a fuel cell, hydrogen as a fuel gas supplied to an anode which is one reaction electrode and oxygen in an oxidant gas supplied to a cathode which is another reaction electrode are electrochemical The energy for reaction is extracted as DC power and heat.

It is well known that when the fuel cell runs short of hydrogen at the anode electrode for some reason during operation of the fuel cell, the voltage characteristics of the fuel cell deteriorate and irreversible deterioration occurs depending on the situation. In order to avoid such a situation of hydrogen shortage operation of the anode electrode, generally, the fuel gas supplied to the anode electrode is supplied in excess of the minimum required reaction gas amount according to the electric load level. There is.

By the way, the hydrogen utilization rate U is used to represent the excess rate of the fuel supplied to the anode. The hydrogen utilization rate U is defined by the following equation (1).

[0005]

[Equation 1] Hydrogen utilization rate U (%) = (amount of hydrogen consumed at the anode electrode / amount of hydrogen supplied to the anode electrode) × 100 …………………… (1)

The hydrogen utilization rate U is used as an index for avoiding hydrogen shortage operation at the anode. Generally, the relationship between the hydrogen utilization rate U and the battery output is that the vertical axis indicates the battery output and the horizontal axis indicates the hydrogen utilization rate. If U is taken, it is shown in FIG. 8, and when the hydrogen utilization rate U becomes L or more, the output sharply decreases. Therefore, it is necessary to lower the hydrogen utilization rate U of the reactant to the hydrogen utilization rate L point or less and operate. In this way, the hydrogen shortage operation is prevented from occurring at the anode electrode by operating so that the hydrogen utilization rate U does not exceed the predetermined reference value.

Conventionally, as an example of means for avoiding hydrogen shortage operation, the output current and the flow rate of gas supplied to the anode are measured as shown in JP-A-63-51060, and the output current is calculated according to Faraday's law. A means for estimating the hydrogen utilization rate from the hydrogen consumption rate and the hydrogen supply rate calculated from the flow rate of the gas supplied to the anode, and issuing a system shutdown command when the hydrogen utilization rate exceeds a predetermined reference value. Was adopted.

FIG. 9 shows the structure of the conventional fuel cell power generator described above.

The fuel cell body 1 comprises an anode electrode 2 which is one reaction electrode and a cathode electrode 3 which is the other reaction electrode. A fuel gas is supplied from the fuel gas supply device 4 to the anode 2, and an oxidant gas is supplied from the oxidant gas supply device 5 to the cathode 3, and the fuel gas and the oxidant gas are electrochemically supplied. It reacts to and generates electricity. The current value during power generation is measured by the ammeter 6 and the flowmeter 7
Measures the flow rate of the fuel gas supplied to the anode 2.

The controller 8 calculates the amount of hydrogen consumed in the anode 2 from the current value measured by the ammeter 6, and further supplies the hydrogen to the anode 2 from the fuel gas flow rate measured by the flow meter 7. Calculate the amount of hydrogen generated. Then, the hydrogen utilization rate is estimated from the amount of hydrogen supplied to the anode electrode 2 and the amount of hydrogen consumed at the anode electrode 2, and the hydrogen utilization rate becomes equal to or higher than a predetermined reference value so as not to perform a hydrogen shortage operation. In this case, the operation stop command was output.

[0011]

However, since it is difficult to accurately obtain the hydrogen utilization rate in the conventional apparatus, there is a problem that there is a high risk of falling into hydrogen shortage operation.

That is, first, in the above-described estimation of the hydrogen utilization rate based on the fuel gas flow rate, the hydrogen utilization rate is correctly estimated if the gas composition of the fuel gas (the concentration of hydrogen contained in the fuel gas) is constant. It is possible. However,
In general, the fuel gas supply device 4 is often of a type in which methane or other hydrocarbon fuel is converted into hydrogen-rich gas for battery supply by steam reforming or the like and supplied. In such a fuel gas supply device 4, since the fuel reforming rate changes depending on the load level, the composition of the fuel gas flowing into the anode 2 usually changes depending on the load level. Further, when a rapid load change occurs, the reforming rate of the fuel gas supply device 4 generally does not follow up so that the composition of the fuel gas supplied to the cell changes transiently. If there is such a change in the fuel gas composition (concentration of hydrogen contained in the fuel gas), the correct hydrogen amount cannot be obtained even if the gas flow rate is measured, so it is not possible to calculate the hydrogen utilization rate accurately. There was a problem that it was difficult.

Secondly, exhaust gas (including unconsumed hydrogen) of the anode electrode 2 is often recycled to the inlet side of the anode electrode 2 in order to effectively use the fuel gas, but such recycling is performed. When used, the change in fuel gas composition at the inlet of the anode 2 due to load level is
It became even larger, and it was difficult to calculate the hydrogen utilization rate accurately because the correct amount of hydrogen could not be obtained by measuring only the flowmeter. As described above, depending on the load level of the fuel cell or in the transient state of the load change, the hydrogen utilization rate is not correctly estimated, and depending on the situation, the hydrogen shortage operation exceeding the predetermined reference value may occur. .. Particularly, there is a problem in that the higher the efficiency of battery power generation with a hydrogen utilization rate close to an allowable upper limit at a high load level, the higher this risk becomes.

Therefore, an object of the present invention is to provide a fuel cell power generator capable of avoiding anode hydrogen shortage operation by obtaining an accurate hydrogen utilization rate during load operation.

[0015]

According to a first aspect of the present invention, there is provided a fuel cell power generation device in which an oxidant gas is supplied to a cathode electrode and a fuel gas containing hydrogen is supplied to an anode electrode to generate electric power. Hydrogen concentration detector that detects each hydrogen concentration of gas on the inlet side of the electrode and gas on the outlet side and outputs each hydrogen concentration detection signal, and hydrogen utilization by the hydrogen concentration detection signal of each gas on the inlet side and the outlet side Calculating means for calculating the rate and outputting a hydrogen utilization rate signal; reference value setting means for outputting a predetermined reference value setting signal; and comparing the predetermined reference value setting signal and the hydrogen utilization rate signal for deviation A comparison means for outputting a signal and a signal output means for outputting an alarm signal and a system stop signal according to the deviation signal for protecting the fuel cell are provided.

According to a second aspect of the present invention, in a fuel cell power generator for supplying electric power by supplying an oxidant gas to a cathode electrode and a fuel gas containing hydrogen to an anode electrode, a gas at an inlet side of the anode electrode is provided. And a hydrogen concentration detector that detects each hydrogen concentration of the gas on the outlet side and outputs each hydrogen concentration detection signal, and calculates the hydrogen utilization rate from the hydrogen concentration detection signals of each gas on the inlet side and the outlet side to calculate the hydrogen utilization rate. A calculating means for outputting a utilization rate signal, a reference value setting means for outputting a predetermined reference value setting signal, and a comparing means for comparing the predetermined reference value setting signal and the hydrogen utilization rate signal and outputting a deviation signal. Further, in order to protect the fuel cell, there is provided a protection control means for carrying out protection control by suppressing the hydrogen utilization rate within a predetermined value based on the deviation signal.

[0017]

With the above structure, the hydrogen concentration of each of the gas on the inlet side and the gas on the outlet side of the anode is detected by the hydrogen concentration detector, and each hydrogen concentration detection signal is output. The calculation means calculates the hydrogen utilization rate from each hydrogen concentration detection signal and outputs the hydrogen utilization rate signal, and the comparison means compares the hydrogen utilization rate signal with a predetermined reference value setting signal and outputs a deviation signal. .. As a result, according to the first aspect of the invention, the alarm signal is output according to the magnitude of the deviation signal, and further the system stop signal is output. Further, in the invention of claim 2, the hydrogen utilization rate is suppressed within a predetermined value based on the deviation signal. Therefore, hydrogen shortage operation at the anode is prevented, and deterioration and deterioration of battery characteristics can be avoided.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a fuel cell power generator showing a first embodiment of the present invention. The same reference numerals as those in FIG. 9 indicate the same or corresponding portions, and the difference from FIG.
Instead of the flowmeter 7 and the controller 8A, the controller 8B, the anode inlet hydrogen concentration meter 9, the anode outlet hydrogen concentration meter 10, the alarm display device 12, and the system stop control device 14
It is a point equipped with and.

The anode inlet hydrogen concentration meter 9 detects the hydrogen concentration at the inlet of the anode 2 and outputs a detection signal. The anode outlet hydrogen concentration meter 10 detects the hydrogen concentration at the outlet of the anode 2 and outputs a detection signal. Control device 8B
Input the detection signals of the anode inlet hydrogen concentration meter 9 and the anode outlet hydrogen concentration meter 10 to obtain the hydrogen utilization rate U.
Is calculated, the hydrogen utilization rate U is compared with the reference value setting signal 11, and an alarm signal 13 and a system stop signal 15 are output according to the magnitude of the deviation signal.

Here, a formula for the controller 8B to calculate the hydrogen utilization rate U only from the hydrogen concentrations detected by the anode-electrode inlet hydrogen concentration meter 9 and the anode-electrode outlet hydrogen concentration meter 10 will be specifically described.

Since the amounts of substances other than hydrogen and water in the composition of the fuel gas passing through the anode 2 do not change, the following equation (2) is established.

[0023]

## EQU00002 ## F1 * (1-X1-X1 ') = F2 * (1-X2-X2') ... (2)

Here, F1; anode inlet flow rate [kmol / h] X1; anode inlet hydrogen molar concentration [molar fraction] (wet base) X1 '; anode inlet water molar concentration [molar fraction] (wet Base) F2; Anode outlet flow rate [kmol / h] X2; Anode outlet hydrogen molar concentration [molar fraction] (wet base) X2 '; Anode outlet water molar concentration [mol fraction] (wet base)

The above equation (2) is rearranged into the following equation (3).

[0026]

## EQU00003 ## F2 = (1-X1-X1 ') / (1-X2-X2') ... (3)

On the other hand, the hydrogen utilization rate U is defined by the following equation (4).

[0028]

## EQU00004 ## U = (F1.times.X1-F2.times.X1 ') / (F1.times.X1) ......... (4)

By substituting F2 of the equation (3) into the above equation (4) and rearranging, the following equation (5) is obtained.

[0030]

## EQU00005 ## U = (X1-X1.times.X2'-X2 + X1'.times.X2) /X1.times. (1-X2-X2 ') .... (5)

By the way, since the hydrogen concentration measured by the hydrogen concentration meter is the hydrogen concentration in the composition other than water, that is, the dry base, the concentrations measured by the anode electrode inlet hydrogen concentration meter 9 and the anode electrode outlet hydrogen concentration meter 10 are When the equation is derived so as to express the hydrogen utilization rate U by using the equation, the following relational equations (6) and (7) are established.

[0032]

## EQU6 ## X1 = Xi (1-X1 ') ... (6) X2 = Xe (1-X2') ... (7)

Here, Xi: anode inlet hydrogen concentration measured by anode inlet hydrogen concentration meter [molar fraction]
(Dry base) Xe; Anode outlet hydrogen concentration [molar fraction] measured with anode outlet hydrogen concentration meter (dry base)

Next, the above equations (6) and (7) are transformed into the equation (5).
Substituting into and rearranging, the following equation (8) of the hydrogen utilization rate U is obtained.

[0035]

## EQU00007 ## U = (Xi-Xe) / Xi (1-Xe) ......... (8)

In the present embodiment, the hydrogen utilization factor U is accurately calculated using the above equation (8).

With the above structure, the hydrogen concentration meter 9 for the anode entrance
And the detection signals of the anode electrode outlet hydrogen concentration meter 10 are input to the controller 8B. The control device 8B performs processing as in the example shown in FIG.

First, the controller 8B reads the values of the detection signals of the anode inlet hydrogen concentration meter 9 and the anode outlet hydrogen concentration meter 10 (101). Then, the control device 8B calculates the hydrogen utilization rate U by the above equation (8). That is, the inlet hydrogen concentration Xi of the anode 2 and the anode 2
The hydrogen utilization rate U is calculated from the outlet hydrogen concentration Xe of Eq.

Next, the value V of the reference value setting signal 11 and the predetermined value α which defines the preset system stop condition are read (103), and the hydrogen utilization rate U and the value V of the reference value setting signal 11 are read.
Is compared to determine which is larger (104). As a result, when the hydrogen utilization rate U is larger than the value V of the reference value setting signal 11, the alarm signal 13 is output to the alarm display device 12 (105). Further, when the hydrogen utilization rate U is larger than the value obtained by adding the predetermined value α to the value V of the reference value setting signal 11, the system stop signal 15 is output to the system stop controller 14 (107).

In the present embodiment, even the fuel gas supply device 4
Even if the fuel gas composition changes depending on the load level or in the transient state due to the load characteristics of, the hydrogen utilization rate is detected more accurately than before, so the comparison with the predetermined reference value is performed accurately, and hydrogen utilization is When the rate U becomes equal to or higher than the reference value, the control device 8B can accurately output the alarm signal or the system stop signal. As a result, the operator can recognize from the alarm that the anode 2 is in a hydrogen shortage operating state, and can perform a system stop operation or the like to avoid the hydrogen shortage in the anode electrode.

Further, by using the system stop control device 14 to automatically stop the system, it is possible to avoid a hydrogen shortage state in the anode 2. Therefore, under any load operation condition, hydrogen deficiency operation of the anode can be avoided, and deterioration and deterioration of battery characteristics can be prevented.

FIG. 3 shows a second embodiment of the present invention.

3 is different from FIG. 1 in that a switching device 16 for switching gas concentration detection lines from the inlet and the outlet of the anode 2 and one hydrogen concentration meter 17 are provided.
In the first embodiment, two hydrogen concentration meters were installed at the inlet and the outlet of the anode 2 in order to measure the hydrogen concentration of the anode 2. However, in this embodiment, the switching device 16 is provided so that the controller 8C can control the hydrogen concentration. The hydrogen concentration meter 17 is switched by the switching signal. In this way, the hydrogen concentration meter required for measuring the hydrogen concentration at the inlet and outlet of the anode electrode 2 can be implemented in the same manner as in the first embodiment even if only one hydrogen concentration meter is used.

FIG. 4 shows a third embodiment of the present invention.

3 is different from FIG. 3 in that the hydrogen utilization rate U calculated from the hydrogen concentration at the anode inlet and the outlet measured by the anode inlet hydrogen concentration meter 9 and the anode outlet hydrogen concentration meter 10 in the controller 8D. And a reference value set in advance are calculated, and the control device 8 is selected according to the deviation level.
Signal 1 to the power generation output control device 18
That is, 9 is generated.

In FIG. 4, two hydrogen concentration meters are installed, one at the inlet and one at the outlet of the anode electrode, but as shown in FIG. The hydrogen concentration may be measured and the hydrogen utilization rate may be calculated.

In the present embodiment, even when the hydrogen utilization rate is close to a preset reference value and there is a risk of falling into a hydrogen shortage operation, the hydrogen utilization rate is maintained while the power generation operation is continued unlike the above embodiments. And has the effect of avoiding hydrogen shortage operation at the anode 2. That is, in the control device 8D, when the calculated hydrogen utilization rate U becomes excessive, the power generation load reduction signal 19 is generated according to the deviation level between the hydrogen utilization rate U and a predetermined reference value.
This reduces the power generation load, so that the anode electrode 2
The hydrogen consumption at is reduced. Therefore, the hydrogen utilization rate U decreases, so that the hydrogen shortage operation can be avoided, the load is reduced under any load operation state, and the anode hydrogen shortage operation is avoided to prevent the deterioration and deterioration of the battery characteristics. Such driving becomes possible.

FIG. 5 shows a fourth embodiment of the present invention.

In this embodiment, the anode gas supply gas flow rate control valve 2 is connected to the fuel gas line supplied to the anode electrode 2.
0 is provided, and the controller 8E adjusts the anode electrode supply gas flow rate control valve 20 to increase or decrease the anode electrode supply gas flow rate according to the deviation level between the hydrogen utilization rate U and a predetermined reference value. .. In FIG. 5, two hydrogen concentration meters are installed, one at the anode electrode inlet and one at the anode electrode outlet. However, as shown in FIG.
The hydrogen utilization rate U may be calculated by measuring the hydrogen concentration at the inlet and outlet of the anode.

In the present embodiment, when the hydrogen utilization rate U becomes excessively large in the control device 8E, this hydrogen utilization rate U
Since the flow rate of the gas supplied to the anode 2 is increased according to the deviation level from the predetermined reference value, the flow rate of hydrogen supplied to the anode 2 is increased and the hydrogen utilization rate is reduced. Therefore, the effect of avoiding the hydrogen shortage operation can be obtained, and the same effect of the invention as the third embodiment can be obtained.

FIG. 6 shows a fifth embodiment of the present invention.

In this embodiment, the anode recycle flow control valve 21 and the anode recycle blower 22 are arranged in the anode recycle line, and the controller 8 is used.
The opening degree of the anode recycle flow control valve 21 is increased or decreased so that F increases or decreases the anode recycle flow according to the deviation level between the hydrogen utilization rate U and a predetermined value.

Although the anode recycle flow rate control valve 21 in FIG. 6 is installed on the outlet side of the anode recycle blower 22, it may be installed on the inlet side. Further, in order to increase the anode recycle flow rate without using the flow rate control valve, the rotation speed variable control of the anode recycle blower 22 may be performed. Furthermore, FIG.
As described above, the hydrogen concentration U at the inlet and the outlet of the anode electrode is measured by one hydrogen concentration meter and a switch, and the hydrogen utilization rate U is obtained.

In the present embodiment, when the hydrogen utilization rate U becomes excessive, the anode recycling flow rate is increased in accordance with the deviation level between the hydrogen utilization rate U and a predetermined reference value, so that it flows into the anode. The fuel gas flow rate is increased and the internal utilization of hydrogen is reduced. Therefore, there is the same effect of the invention as in the third and fourth embodiments in that hydrogen shortage operation can be avoided.

FIG. 7 shows a sixth embodiment of the present invention.

In this embodiment, the fuel gas supply device 4
A reformer 23 for performing a reforming reaction for converting methane or other hydrocarbon fuel into hydrogen-rich gas and a reformer controller 24 for controlling the reforming temperature in the reformer are provided as It is configured to generate a signal for raising the reforming temperature to the reforming system control device 24 according to the deviation level from a predetermined reference value. As a result, since the reforming main reaction and the endothermic reaction in the reformer 23 are performed, the reforming temperature is raised and the amount of conversion from hydrocarbon to hydrogen is increased.

In FIG. 7, in the present embodiment, when the hydrogen utilization rate U becomes excessive, the reforming temperature is raised according to the deviation level between the hydrogen utilization rate U and a predetermined reference value. Increase the conversion of hydrocarbons to hydrogen. As a result, the amount of hydrogen flowing into the anode electrode can be increased and the hydrogen utilization rate can be reduced, so that the same effects as the third to fifth embodiments can be obtained. Two hydrogen concentration meters are installed, one at the inlet and one at the outlet of the anode. As shown in Fig. 3, the hydrogen concentration at the inlet and outlet of the anode is measured by one hydrogen concentration meter and switch, and hydrogen is used. You may ask for the rate. Further, the calculation of the hydrogen utilization rate U is not always the above equation (8).
The hydrogen utilization rate is not limited to that according to the above, and the hydrogen utilization rate may be approximately calculated based on the hydrogen concentration at the inlet side and the outlet side of the anode 2.

[0058]

As described above, according to the present invention, the hydrogen concentration of each of the gas on the inlet side and the gas on the outlet side of the anode electrode is detected to accurately calculate the hydrogen utilization rate, and this value and a predetermined reference value are used. A warning signal or a system stop signal is generated according to the deviation from the value, or a means for performing a protection control to reduce the hydrogen usage rate according to the deviation between the hydrogen usage rate and the reference value is provided. Also, the hydrogen shortage operation of the anode electrode can be avoided, and the deterioration and deterioration of the battery characteristics can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel cell power generator showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of FIG.

FIG. 3 is a configuration diagram of a fuel cell power generator showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a fuel cell power generation device showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a fuel cell power generator showing a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a fuel cell power generator showing a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a fuel cell power generator showing a sixth embodiment of the present invention.

FIG. 8 is an explanatory view showing the relationship between hydrogen utilization rate and battery voltage.

FIG. 9 is a configuration diagram of a fuel cell power generator showing a conventional example.

[Explanation of symbols]

 1 Fuel cell main body 2 Anode electrode 3 Cathode electrode 4 Fuel gas supply device 5 Oxidant gas supply device 9 Anode electrode hydrogen concentration meter 10 Anode electrode hydrogen concentration meter 11 Reference value setting signal 12 Alarm display device 13 Alarm signal 14 System stop Controller 15 System stop signal

Claims (2)

[Claims] 1. A fuel cell power generator for supplying an oxidant gas to a cathode electrode and a fuel gas containing hydrogen to an anode electrode to generate electric power, wherein a gas on an inlet side and a gas on an outlet side of the anode electrode Hydrogen concentration detector that detects each hydrogen concentration and outputs each hydrogen concentration detection signal, and calculates the hydrogen utilization ratio from the hydrogen concentration detection signal of each gas on the inlet side and outlet side and outputs the hydrogen utilization ratio signal Calculating means, a reference value setting means for outputting a predetermined reference value setting signal, and a comparing means for comparing the predetermined reference value setting signal with the hydrogen utilization rate signal and outputting a deviation signal,
A fuel cell power generation device comprising: a signal output unit that outputs an alarm signal and a system stop signal according to the deviation signal to protect the fuel cell. 2. A fuel cell power generator that supplies an oxidant gas to a cathode electrode and a fuel gas containing hydrogen to an anode electrode to generate electric power, wherein a gas on the inlet side and a gas on the outlet side of the anode electrode Hydrogen concentration detector that detects each hydrogen concentration and outputs each hydrogen concentration detection signal, and calculates the hydrogen utilization ratio from the hydrogen concentration detection signal of each gas on the inlet side and outlet side and outputs the hydrogen utilization ratio signal Calculating means, a reference value setting means for outputting a predetermined reference value setting signal, and a comparing means for comparing the predetermined reference value setting signal with the hydrogen utilization rate signal and outputting a deviation signal,
In order to protect the fuel cell, the fuel cell power generator is equipped with a protection control means for controlling the hydrogen utilization rate within a predetermined value based on the deviation signal.